1. Field of the Invention
The present invention relates in general to a method for manufacturing a speaker diaphragm, and more particularly to a method for manufacturing a speaker diaphragm having a pseudo-textile fabric made by arranging carbon yarns or other yarns to come in tangential contact with a plurality of virtual concentric circles so as to eliminate a directional property due to a cross structure of warps and wefts of a prior fabric and to reduce divided vibrations.
2. Description of the Prior Art
In general, a speaker for amplifying and reproducing sounds converts an electrical energy input through a coil to a mechanical vibration energy, and thereby generating sounds. Therefore the shape and the material of a speaker diaphragm are very important factors to decide quality of sounds.
The method for manufacturing a conventional speaker diaphragm using a carbon cloth or an aramid cloth comprises the steps of impregnating a carbon cloth or an aramid cloth with a thermosetting resin and forming a shape of diaphragm from the impregnated cloth. The resultant diaphragm have a rigidity necessary for maintaining the shape of itself since the fibers of the impregnated cloth are bound by a cure of the resin used as a binder.
Forming process is performed by using a mold consisting of an upper part and a lower part. There are voids in the vicinity of intersection points of warps and wefts. The front side or the rear side of the diaphragm is coated with a resin to prevent an air from leaking through the voids.
The conventional speaker diaphragm uses generally a carbon cloth or an aramid cloth having a more higher elastic modulus as it's a material. Because the material is a textile fabric woven by a plain weave method, it is inevitable for the fabric to have a directional property due to the directions of warps and wefts when the fabric is used as the material of the diaphragm.
That is, in the conventional speaker diaphragm, the arrangement directions of yarns(warps and wepts) constituting a textile fabric can not include the all directions of the diaphragm. Therefore according to the arrangement direction of the yarns, the flexural rigidity of the diaphragm, the propagation velocity of a sound and so on become different. This hinders in piston motion of the diaphragm caused by the vibration of a speaker and generates the divided vibrations.
When the divided vibrations are generated from the lower frequency band, sound distortions are generated in higher frequency band as well as in the lower frequency band. As a result, the definition of sound are deteriorated.
In order to avoid the above-mentioned directional property, it is necessary to provide a textile fabric woven in radial. However, it is very difficult to weave the radial fabric.